Avalanche Disk Granular Physics Demonstrator

Build your own avalanche disk to observe granular physics in action. A single granule is a solid but when it interacts with many, it may behave as a solid, liquid, or gas.

I first saw one of these a while back in some science museum that I took Caitlin to. It was more of an art installation where I thought the inside was like one of those lava lamp fluid things. I recently saw a related video to an avalanche disk and it looks like The Museum of Science and Industry - Chicago has one on display. Theirs is 20 ft in diameter and weighs several tons. This one scaled way down. It's one of those things - "How did they do that?" but more importantly, "Can you make it at home?" Other than that, there is a field of science that applies to this.

Learning Objective: Build and use an avalanche disk to observe the behavior of granular solids as granules flow, shear, mix, separate and freeze.

Knowing how granular solids act is pertinent to helping you predict/prevent snow avalanches to designing machines to package your cereal. Computer modelling can be quite complex.

Added Note: This may have been what I really saw, Rheoscopic fluid. Great ible on it too.https://www.instructables.com/id/Making-Rheoscopic...

Video of the Avalanche Disk in action (overdub with your best Carl Sagan impression on the creation of the universe):

Step 1: Apparatuses or Apperatii?

You will need:

Some sort of rotating base:
I found this rotating artist's turnstyle stand at a discount store. The rotation is manually powered by hand but something like a motorized potter's wheel or old-fashioned LP record player turntable(don't know if it has enough torque for heavy loads) would be better. I was thinking of attaching my container to a sanding disk that is chucked up in a power drill. You can also build a rotatable base with a lazy-susan turntable or mechanism (IKEA has lazy-susan turntables - I was planning to make a wheel of fortune or casino spinner with one)

Some sort of container for your media:
I found this clear plastic half dome container for storing lettuce halves. It has a dome cover I could put on but any round flat bottom container with a low wall would suffice. A cover is nice so you don't have a toxic spill with the media. You can use the upper half of a CD/DVD spindle cover.

Granular solids:
The museum exhibit description says it uses a mix of glass beads and red garnet sand. I do not know what size grain they use but I remember ibles using glass microbeads for its reflective properties. Harbor Freight is a source for a bulk amount of glass microbeads. I got the smallest(25lb container, around $25 US) of 80 grit glass microbeads used for sandblasting. The stuff feels like a smooth powder and is quite fine. The craft store that sells you a thimble full for glitter work is too expensive. I don't think you would want to inhale any of it and getting some on the floor makes it a slipping hazard. Keep it contained and work deliberately with it. I think I only used a few ounces of the product and have a lot to use on other projects such as painting a reflective stripe in my driveway(this may be the stuff they dust the street white lines after painting).

I also got a bag of red colored play sand, the stuff used for sand sculptures you fill in bottles. It is also quite fine in texture.

Step 2: Simple Setup

Pour a layer of the glass microbeads in your base container.

Tilt is so that you can see the "sand" flow down like sand dunes.

Add enough so that the entire bottom is covered and there is still a layer where portions of the avalanche slide down.

Add a top layer of red sand.  You might just want to add a small portion at first to see what kind of effect you get when you actually run the experiment.  Add more for better contrast.

Step 3: Affix to Turntable

I just taped my container to the rotating turntable.

Adjust the angle of the turntable.  Adjust so that the "sand" just starts to slide down.

This angle may be anywhere from 20 to 30 degrees. 

Start the rotation.

Step 4:

Experiment with rotating the Avalanche Disk at different speeds.

Experiment with different angles or slope of the terrain.

Experiment with different media, maybe substitute sugar, salt, flour, baking soda, and kool-aid or flavored drink mix as the coloring agent.

Observe how granular solids behave en masse  as a solid, liquid, or a gas.  Note the vortex-like flow patterns. Record and discuss your findings.

Why doesn't it all mix into one homogenous mix of pink sand?  Why does it separate out at points?

What happens when you introduce obstacles to interrupt or divert the natural flow?

I think I might get some blue sand to make an event horizon insert into my Stargate Gong and turn it into a coffee table.

Cool!